The tallest building in Wales completed 2009 by Carillion PLC has endured several years of “opening up” of internal walls and ceilings, finding areas of incomplete fire stopping and completing necessary remedial work. In late 2017 attention turned to the external cladding and the suitability of the external fire barriers. R. Lewis & Co (UK) Ltd were commissioned to find a solution to remediate failings in the external barrier. The cladding system is an SPS Envirowall render system that required Rockwool Lamella to be fixed and adhered to the slab edge creating a continuous seal. On inspection it was found that the original adhesive was ‘dot and dabbed’ to the external slab edge creating hidden voids behind the Lamella.
The brief was to create a solution that would fill the required gap without the need to remove the render system completely. An urgent fire test date was provided at BRE’s Burn Hall in Watford. On January 5th the concept was presented to the project team and demonstrated at R. Lewis HQ with a test rig assembled and prepared ready for test January 17th.
Unfortunately, on January 15th and just days before the test due date Carillion PLC went into liquidation. Acknowledging the possibilities of the system solution offered and with full faith in the system being able to pass the planned fire test, R. Lewis & Co (UK) Ltd took full responsibility for this test and arranged for the programme to continue.
The test was successful, and the R. Lewis FBI system is about to be implemented as a solution on this project.
A 28 – storey residential building with a restaurant situated on the top 2 floors was found to have significant breaches behind each external slab ‘floor break’. The external cladding is a rendered SPS Envirowall system (see Images 1, 2, & 3)
Image 1 – Cutting in through the render at slab level
Image 2 – Marker pen on the slab shows the size of the dabs of adhesive and the gaps between them, some up to 400mm.
Image 3 – At times the void was up to 40mm deep creating the potential for hot gasses to pass between floors unnoticed.
External work is made more difficult due to the height of the building and its location on the Swansea coastline, where the environment changes hourly. Experts and advisors to Carillion had said that the only acceptable option was to cut the render away in whole 200mm wide strips and replace the existing fire barrier as per the cladding manufacturers tested criteria.
This was estimated to take 3 years and cost in the region of £12m and by fixing the fire barrier this way it would significantly damage the weather seal to the building.
With a proven track record in design and creation of bespoke solutions for live fire test situations for Carillion, R. Lewis & Co (UK) Ltd were commissioned by the project team to provide an alternative solution to that of complete removal of the existing cladding system.
As the area concerned comprised of a void hidden behind a product that is tried and tested for this type of installation, it seemed that the logical solution would be to inject the void behind the Rockwool, between the ‘adhesive dot and dab method’. Several methods were tried, expanding foam, like for like adhesive, mastics, fire rated mortar compound, etc.
The problem with injection of materials without being able to view the flow or as a ‘blind side’ install, is how can you guarantee the seal ratio. The only product that appeared to satisfy all the requirements was the R. Lewis FBI System. We were able to inject the product with a good flow ratio, it had good adhesive properties and if there were any small gaps to fill it had been tested to expand sufficiently in its cured state in all directions.
A mock up wall was created and the main contractor, their expert witness and Exova all visited our Research and Development facility to witness this latest installation method. All agreed that this ‘solution’ was viable and could be put forward for a BRE BS 8414 test.
Given the high-profile and costs associated with this project the building’s owners employed their own expert witness who would shadow the project and agree certain parameters such as how the bespoke tests should be set up to best mimic the conditions found on site.
As the maximum void found on site was 400mm wide, 40mm deep. It was agreed that the test rig would be designed to accommodate a 500mm x 50mm void at one of the slab heights. The average on-site construction dimensions were around 250mm x 20mm, so the other slabs were formed with a 500mm x 25mm void. It was agreed that these conditions would be the most onerous and would exceed the worst case found on site.
See image 4, 5 & 6.
Image 4 – The test rig
Image 5 – Building in the voids at the slab edge.
Image 6 – CAD detail of the test rig build.
Once the build was complete, we then employed a specialist to render the wall to match the conditions found on site. To make the install more robust we drilled agreed centres at the slab edge and injected the R. Lewis FBI System. The purpose of this, was to represent the situation where by we did not know where the ‘dot and dabs’ were and to recreate the injection process as it would need to be on site. Once injected the render was also patched repaired as it would be after the injection method was complete on site. See images 7, 8 and 9
Image 7– Render drilled at agreed centres.
Image 8 – HPE injected into the holes.
Image 9 – Render patch repaired as it would be on site shows the works will be seamless when complete.
The whole system was left to cure as well as it could have been given, the freezing temperatures in January. Two days before the test was scheduled Carillion the main contractor went into liquidation throwing the entire test into doubt. Given the seriousness of this problem on site and that so much time and effort had gone into getting this concept build put together and ready for the fire test, R. Lewis & Co (UK) Ltd took the responsibility for the test and proceeded to include shouldering the full cost of the build and the test.
Following the Grenfell tragedy, DCLG, had almost taken over the burn hall, that coupled with the biggest manufacturers retesting their cladding systems, we were extremely lucky to have this build in the fire test rig. A rescheduled test could have taken another 12 months to rearrange and potentially meant that the residents in the tower would be waiting a year not knowing if their building could be made safe using this method.
The test went ahead on 17th January 2018, the fire test lasted the full 60 minutes and it was clear to all witnessing the burn that the system had performed well.
The R. Lewis FBI System had done just as we had expected and filled the voids without slumping down the wall during the initial injection process. It had also expanded dramatically when in contact with the direct heat during the test. What wasn’t expected was that the R. Lewis FBI System also ‘caught’ falling debris from the upper floors of the rigged construction.
See images …….
Image 10 – 5 mins into the fire test
Image 11 – 27 mins into the fire test
Image 12 – Aftermath showing damage of the patch repair only.
The following day we started with de-rigging of the system. BRE would work with us to document each stage looking for hidden damage and failures. As image 14 shows while the polystyrene burnt away directly above the combustion chamber the R. Lewis FBI System and Lamella combination stopped some of the heat spread at the second level and the polystyrene was still intact at the highest point. It was clear that the hidden void had indeed been sealed. The internal linings at each level were completely untouched and only recorded a temperature of 36 degrees while the temperature in the combustion chamber reached 1000 degrees.
Image13 – Aftermath under the render.
This is the only system of its type and is unique in that the installer not only designed the concept but owns the test data for the installation method.
We believe that following Grenfell, the current climate surrounding cladding failures has led to much confusion and is mainly due to a focus on ACM systems.
There are hundreds of buildings in the UK alone with this type of cladding with no obvious solution to possible fire risk issues. This type of exposure and endorsement from the ASFP of the R. Lewis FBI system will help local authorities and residents who could be looking at huge remedial costs to consider remediation of an existing and potentially salvageable system or who perhaps may already be waiting to test a very similar method that is available now and ready to use.